Use fingerprint when min_sdk is current or none

We have versions of the same apex targetting different min_sdk_versions;
however, fingerprint is overriding the hardcoded min_sdk_version. We
should only be overriding if it is current or unset.

Test: go test apex soong tests
Change-Id: Id030a5ba7d8edebb806ce83d318132fd839a00a5